This creates a blank FirstViewController instance — one completely unconnected with the interface you designed in the storyboard. Its view is empty. It has no table view in it. Therefore, since there is no table view, there is no outlet connection from any table view, and listTableView remains nil.

What you want to do is get the FirstViewController instance from the storyboard, the one whose interface you have already designed in the storyboard. You can do that by talking to the storyboard and using the FirstViewController's identifier, i.e., call instantiateViewController(withIdentifier:). (You might have to give the FirstViewController in the storyboard an identifier for this purpose.)